About Genetic Inheritance

Most genetic traits, like hair or eye color, are a blend of both parents’ genetics. But when it comes to tracing certain traits to certain parents, genes contained in sex chromosomes play a key role.

Through cell division and fertilization, humans acquire 46 chromosomes containing their unique DNA; 23 from mom, and 23 from dad. Sex-linked genes are expressed according to the genetic material on sex chromosomes, specifically, the 23rd pair, which differ between sexes. Where females have two X chromosomes, males have one X chromosome and one Y chromosome, with certain genetic traits found exclusively on either one.

Even still, some chromosomal genes are dominant or recessive, meaning that whether or not a characteristic is expressed depends on the alleles of mom and dad (respectively). If, for example, dad has an X-linked dominant gene, while mom has an X-linked recessive gene, the daughter’s outward gene expression will reflect dad’s genotype.

What genes are inherited from the father only?

As we now know, genes are inherited from both parents, with each parent contributing half of the genetic material to their offspring. However, certain genetic traits are influenced by specific genes located on the sex chromosomes (X and Y chromosomes), which are inherited differently according to biological sex. Let’s take a look at the physical traits inherited from father to child.

#1 Baby’s Biological Sex

Dads are responsible for the biological sex of their baby. It’s one of the physical traits that’s 100% determined by paternal genes and/or dads.

The Supporting Evidence : While mothers will always pass down their X chromosome (considering it’s the only kind they have), fathers will pass down either an X or Y chromosome at random. The gendered difference is entirely dependent on this one minuscule genetic distinction:

• The Y chromosome contains the SRY (male-determining) gene, which kickstarts the “virilization” (masculinization) process, including the fetal development of the testes—this means you have a baby boy on the way!
• The X chromosome doesn’t contain this male-producing gene,. which means you’re having a baby girl!

The Big Picture : All of the physical differences between boys and girls are due to this tiny chromosomal difference. Dad’s contribution makes a big impact and can significantly affect the different genes your baby will carry!

#2 Height

At least 700 genetic variations are responsible for determining height, coming from both parent’s genes. But, there is evidence to suggest that dad’s genes contribute to growth, while mom’s can regulate it.

The Supporting Evidence: The insulin-like growth factor (IGF protein) is strongly expressed by paternal genes. This genetic trait is also responsible for promoting growth. However, mom’s genes express a somewhat contradictory receptor called IGF2R, which essentially does the opposite by actively repressing dad’s height-inducing genes.

These are both examples of genomically imprinted genes . An imprinted gene is “stamped” or turned off, leaving the other gene to be expressed.

From an evolutionary standpoint., these genetic differences between mom and dad are called “ parent-of-origin effects ,” which have an impact on growth and nutrition:

• Paternal influence – Dad’s evolutionary adaptation wants  the son to grow big and strong in the womb. His genes use imprinting to give off signals during fetal development: “take nutrients from mom so you can be fit enough to survive life outside the womb.” Consuming more nutrients leads to increased growth.
• Maternal influence – Having a baby can certainly be an excessive nutritional demand on Mom-especially in the early ages of human evolution. To counteract this somewhat parasitic relationship, mom’s genes use imprinting to avoid the fetus needing so much sustenance, which can, in turn, suppress growth.

The Big Picture: Beyond the give-and-take of these two specific genetic expressions, there are loads more variants affecting height from both mom and dad. Dad’s genes strongly influence your child’s size in a certain sense, but whether your children grow up to be 6’5″ basketball stars or 5’10” point guards are up to certain genetic conditions from both parents.

#3 Y-Linked Inheritance (for Sons)

All men inherit a Y chromosome from their father, which means all traits that are only found on the Y chromosome come from dad, not mom.

The Supporting Evidence : Y-linked traits follow a clear paternal lineage. A mutation on the Y chromosome can only be passed from father to son, and they’re all considered “dominant” in that there’s no second Y chromosome from mom to alter or mitigate the effects.

In addition to the male traits of sperm development, hormone levels, and other distinctly male physical characteristics, there are other non-gendered Y-linked traits :

• Hypertrichosis – Excessive hair growth on the outer ear
• Syndactyly – “Webbed toes,” where the skin between one or more toes is fused
• Chromosome infertility – Can affect the male’s sperm production

The Big Picture : For the most part, there’s no real indication that boys take after their dads in looks any more than they look like mom, but Y-linked traits are the exception to this rule.

# 4 X-Linked Inheritance (for Daughters)

As we’ve learned, fathers contribute one Y or one X chromosome to their offspring. Daughters receive an X chromosome from each parent, inheriting a mix of X-linked genes from her father as well as her mother.

When your daughter inevitably ends up with his X chromosome, does that mean she’ll inherit all of his X-linked genes and traits?

Genes, yes. Traits, not necessarily.

The Supporting Evidence : When it comes to a trait passed from father to daughter, dad has a 100% chance of passing down any mutations or variations on his X chromosome. However, this doesn’t automatically mean that all of these characteristics will present physically.

While dad is passing down everything on his X chromosome, mom is also giving their daughter a second copy. Only one copy of the allele (variation or mutation in a specific gene) is required for your daughter to develop the characteristic. If dad has the X-linked dominant gene, his daughter will undoubtedly present the trait because she inherits his X chromosome (where the gene responsible for the trait exists).

Some examples of genetic disorders associated with X linked dominant inheritance include:

• Fragile X syndrome
• Oral-facial-digital syndrome type I
• Incontinentia pigmenti type 1.

As for X-linked recessive: conditions,both parents’ chromosomal genes must contain two copies of the recessive trait in order to present physically. Dad’s genes are only half of the equation in this case.

The Big Picture : While X-linked recessive traits are a toss-up between mom and dad’s DNA, X-linked dominant features (when the allele variation is present in the father) is bound to make their way into your little girl’s life.

#5 Fat Storage

There are a number of factors that go into the size and shape of our body, and genetics certainly has a lot to do with it. Dad’s adipose tissue, however, seems to have a bigger role in passing on excess fat compared to mom’s.

The Supporting Evidence : Some body fat is necessary for general health and survival. But, too much can lead to a number of health issues and complications. In the body, there are two types of fat cells that can be considered “good” or “bad.” Brown fat is responsible for burning calories and maintaining a safe body temperature. White fat, on the other hand, stores excess energy (calories) as fat.

Researchers have identified that brown fat is maternally inherited, while white fat is paternally inherited. This means that dad’s genes are more likely to contribute to the development of excess fat.

Some health implications of obesity and excess fat include:

• Heart Disease
• Diabetes
• High Blood Pressure
• Metabolic Syndrome

The Big Picture : Just because dad has a few extra pounds doesn’t mean your baby is destined for a similar fate. An active lifestyle and a healthy diet play a significant role for long-term health and wellness, regardless of parental genetics.

Do Babies Acquire Personality Traits From Their Father?

The question of whether babies acquire personality traits from their father is an intriguing aspect of genetic inheritance. While personality is a matter of both genetic and environmental factors, there is evidence to suggest that certain personality traits can be influenced by genes inherited from the father.

The Supporting Evidence : Research in the field of behavioral genetics has shown that genetic factors play a significant role in shaping individual differences in personality. Traits such as extroversion, introversion, agreeableness, neuroticism, and openness to experience have been found to have a genetic basis.

Studies have identified specific genes associated with certain personality traits, and some of these genes may be inherited from the father only. For example, genes that influence neurotransmitters like serotonin and dopamine can impact mood and emotional regulation, thus influencing aspects of personality and mental health.

The Big Picture : While it is difficult to attribute a baby’s personality solely to genes inherited from the father, there is no denying that genetic factors play a part in shaping personality traits. The interplay of genes from both parents, combined with the child’s unique experiences and environment, creates a rich tapestry of personality that makes each individual special and distinct.

Put the Rumors to Rest with SneakPeek

While you might wind up making a few lucky guesses of your baby’s traits and gender, the only real way to determine how everything shakes out is with genetic testing from a doctor.

However, you can start getting to know your baby with the SneakPeek At-Home Early Gender Blood Test—the only at-home fetal gender test that can tell you whether you are expecting a baby boy or a baby girl as early as 6 weeks into pregnancy! That’s months before a traditional 20-week anatomy ultrasound can tell you (and why our test is trusted by over 1 million moms and top obstetricians). Plus, our results are clinically-proven over 99% accurate.

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